Phosphonic compounds (ethephon) have been used for years as plant growth regulators, harvest aids and defoliation products. Atwater et.al has shown that when ethephon is formulated in sulfuric acid and adduct the Plant Growth Regulated (PGR) effects are increased. The present invention shows that the increased in the PGR effect shown by Atwater occurs with other acids as well as with the sulfuric acid combinations claimed in the Atwater patent(s).